"We are thrilled to have Eric join the cast," executive producer Shane Brennan said. "He has already proved himself to be a great asset and invaluable member of the team, and Eric's fans will be delighted to see what we have in store for him."Olsen has previously appeared on Tru Calling, Brothers & Sisters, and Community. NCIS: Los Angeles returns Tuesday, Sept. 21 at 9/8c.